Graphene first appeared in laboratory in the year of 2004, at that time the two scientists in the University of Manchester, i.e., Andre Jim and Kostya Novoselov, found that they could obtain a graphite flake that became thinner and thinner by a very simple method. That is, they peeled the graphite flake from the graphite, adhered the two sides of the flake onto a special tape, and after tearing the tape, the graphite flake was divided into two flakes. By continuing the above operation, the flake became thinner and thinner. Finally, they obtained a flake only consisted of one layer of carbon atom, that is, graphene. From then on, the method for preparing graphene was emerged abundantly, and currently there are mainly two preparation methods as follows:
1. Arc-Discharge Method. Rao CNR et al firstly used this method to prepare graphene. They use a mixture gas of hydrogen and helium as the reaction gas. The preparation of graphene by this method is dangerous because it needs a high hydrogen pressure and a large discharge current.
2. SiC thermal decomposing method. In this method, the single crystal SiC is heated so as to remove Si by decomposing the SiC on the surface, and the remaining carbon forms graphene. However, the single crystal SiC used in the SiC thermal decomposition is very expensive and the grown graphene is distributed in a shape of island, the porosity is high and the layer is not uniform. Further, when such obtained graphene is subject to structuralization to make various devices, the electron migration rate is low due to the process of photo-engraving or dry-etching etc, thus affecting the performance of the devices.
Further, the existing preparation method of graphene, such as disclosed in Chinese patent application 200810113596.0 (The Preparation of Graphene by Chemical Vapor Deposition) includes, firstly to prepare the catalyst, and then perform a high temperature chemical vapor deposition, that is, the substrate containing the catalyst is placed into an oxygen-free reactor, the substrate is heated to 500-1200° C., then a carbon-containing source gas is flowed in to carry out the chemical deposition to obtain graphene, after that, the graphene is purified by the acid treatment or the vaporization under low pressure and high temperature to remove the catalyst. The main demerits of this method are: the process is complicated, the catalyst needs to be removed, and the exhausting energy is high so lead to a high cost.